Anode materials for lithium-ion batteries

ABSTRACT

The current disclosure relates to an anode material with the general formula M y Sb-M′O x —C, where M and M′ are metals and M′O x —C forms a matrix containing M y Sb. It also relates to an anode material with the general formula M y Sn-M′C x —C, where M and M′ are metals and M′C x —C forms a matrix containing M y Sn. It further relates to an anode material with the general formula Mo 3 Sb 7 -C, where —C forms a matrix containing Mo 3 Sb 7 . The disclosure also relates to an anode material with the general formula M y Sb-M′C x —C, where M and M′ are metals and M′C x —C forms a matrix containing M y Sb. Other embodiments of this disclosure relate to anodes or rechargeable batteries containing these materials as well as methods of making these materials using ball-milling techniques and furnace heating.

PRIORITY CLAIM

The present application is a continuation application of InternationalApplication No. PCT/US2012/051173 filed Aug. 16, 2012; which claimspriority to U.S. Provisional Patent Application No. 61/525,532 filedAug. 19, 2011, and also claims priority to U.S. Provisional PatentApplication No. 61/539,135 filed Sep. 26, 2011, which are incorporatedby reference herein in its entirety.

STATEMENT OF GOVERNMENT INTEREST

The present invention was developed using funding from the United Statesgovernment through Department of Energy Grant No. DE-AC02-05CH11231, andDepartment of Energy Grant No. DE-SC005397. The United States governmenthas certain rights to the invention.

TECHNICAL FIELD

The current invention relates to materials usable as anodes inbatteries, particularly lithium-ion secondary (rechargeable) batteries.The invention also relates to anodes and batteries containing suchmaterials. The invention further relates to methods of making thematerials and anodes and batteries using such materials.

BACKGROUND Basic Principles of Batteries and Electrochemical Cells

Batteries may be divided into two principal types, primary batteries andsecondary batteries. Primary batteries may be used once and are thenexhausted. Secondary batteries are also often called rechargeablebatteries because after use they may be connected to an electricitysupply, such as a wall socket, and recharged and used again. Insecondary batteries, each charge/discharge process is called a cycle.Secondary batteries eventually reach an end of their usable life, buttypically only after many charge/discharge cycles.

Secondary batteries are made up of an electrochemical cell andoptionally other materials, such as a casing to protect the cell andwires or other connectors to allow the battery to interface with theoutside world. An electrochemical cell includes two electrodes, thepositive electrode or cathode and the negative electrode or anode, aninsulator separating the electrodes so the battery does not short out,and an electrolyte that chemically connects the electrodes.

In operation the secondary battery exchanges chemical energy andelectrical energy. During discharge of the battery, electrons, whichhave a negative charge, leave the anode and travel through outsideelectrical conductors, such as wires in a cell phone or computer, to thecathode. In the process of traveling through these outside electricalconductors, the electrons generate an electrical current, which provideselectrical energy.

At the same time, in order to keep the electrical charge of the anodeand cathode neutral, an ion having a positive charge leaves the anodeand enters the electrolyte and a positive ion also leaves theelectrolyte and enters the cathode. In order for this ion movement towork, typically the same type of ion leaves the anode as enters thecathode. Additionally, the electrolyte typically also contains this sametype of ion. For instance, in a lithium-ion battery, the ion that leavesthe anode, enters the cathode, and is found in the electrolyte is alithium ion (Li⁺).

In order to recharge the battery, the same process happens in reverse.By supplying energy to the cell, electrons are induced to leave thecathode and move into the anode. At the same time a positive ion, suchas Li⁺, leaves the cathode and enters the electrolyte and a Li⁺ leavesthe electrolyte and enters the anode to keep the overall electrodecharge neutral.

In addition to containing an active material that exchanges electronsand ions, anodes and cathodes often contain other materials, such as ametal backing to which a slurry is applied and dried. The slurry oftencontains the active material as well as a binder to help it adhere tothe backing and conductive materials, such as a carbon particles. Oncethe slurry dries it forms a coating on the metal backing.

Unless additional materials are specified, batteries as described hereininclude systems that are merely be electrochemical cells as well as morecomplex systems.

Anodes in Lithium-Ion Batteries

In order for a battery to function properly, the materials used in theanode, cathode and electrolyte are typically selected to have compatibleelectrical, chemical, and electrochemical properties. For instance, thematerials may be selected to operate at compatible voltages. Manyrechargeable lithium-ion batteries use carbon, typically in the form ofgraphite, as the anode because of voltage compatibility. Graphite,however, suffers from a number of drawbacks.

First, graphite anodes cause limits in battery properties. For instance,they limit theoretical gravimetic capacity to 372 mAh/g and theoreticalvolumetric capacity to 830 AWL or practical volumetric capacity toaround 350 Ah/L, meaning that a heavier and larger battery is requiredto supply sufficient energy for many applications. In some instances,this does not cause serious problems but in others, where, for example,it results in a much heavier and less-efficient automobile or a heavierlaptop computer, it is a significant drawback.

Second, the surface of the carbon anode is prone to unwanted chemicalreactions with the electrolyte. This can lead to the formation of newchemicals, which are deposited on the surface of the carbon anode in asolid-electrolyte interfacial (SEI) layer. The SEI layer can impedelithium-ion access to the anode and interfere with battery function.

Third, because the charge/discharge potential of carbon anodes in manylithium-ion batteries is close to the potential at which Li⁺ convertsfrom its ionic state back to a metal (Li or Li⁰), Li metal often forms adeposit on the anode. This deposit, like the SEI layer, can impedelithium-ion access to the anode. More importantly, as the Li metaldeposit grows with each charge/discharge cycle, it eventually extendsfrom the anode over to the cathode. Li metal is conductive, so when thisoccurs electrons can move from the anode to the cathode via the Li metaldeposit instead of through the external electrical conductor. When thishappens, the battery short circuits and no longer provides power to thedevice containing the external electrical conductor. As a result, thebattery is no longer useful and must be discarded.

Graphite anodes also experience a fourth problem when used with cathodescontaining manganese, such as manganese oxide spinels. In suchbatteries, manganese slowly leaches from the cathode and enters theelectrolyte where it eventually makes its way to the anode. Once there,it reacts with the anode in very unfavorable manners that eventually“poison” the anode and destroy its ability to participate in thebattery's electrochemical reactions. At this point, the battery is nolonger useful and also must be discarded. This problem associated withcarbon anodes has long hampered the development of lithium-ion batterieswith manganese-based cathodes, many of which are otherwise usefulmaterials.

To address these drawbacks, many alternative anode materials have beenexplored. For instance, anodes using various metals have been createdand tested. Many of these metal-based anodes overcome one or more of thedrawbacks associated with carbon anodes, but, unfortunately, metal-basedanodes often suffer from different drawbacks that similarly render themnon-ideal or otherwise incompatible with useful electrolytes orcathodes. For instance, antimony (Sb)-based anodes exhibit improvedgravimetric and volumetric capacity, but tend to fail or exhibit largecapacity fade after a relatively low number of cycles. This failureresults from physical degradation of the anode because particles of theanode material found in the coating portion of the electrode changevolume substantially between their charged and discharged states. As aresult, these particles become physically detached from other coatingmaterials, such as conductive particles, and otherwise degrade thecoating, resulting in a decrease in anode function and occasionallyeventual anode failure.

SUMMARY

Embodiments of the current invention described in this disclosureovercome one or more drawbacks associated with carbon and previous metalanodes or are otherwise suitable anode materials for use in alithium-ion battery.

In one embodiment, the current invention relates to an anode materialwith the general formula M_(y)Sb-M′O_(x)—C, where M is selected from thegroup consisting of copper (Cu), molybdenum (Mo), nickel (Ni), titanium(Ti), or tin (Sn), and combinations thereof, M′ is selected from thegroup consisting of aluminum (Al), magnesium (Mg), titanium (Ti),vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co),nickel (Ni), zirconium (Zr), molybdenum (Mo), tungsten (W), niobium(Nb), or tantalum (Ta), and combinations thereof, and M′O_(x)—C forms amatrix containing M_(y)Sb.

According to another embodiment, the invention relates to an anodematerial with the general formula M_(y)Sn-M′C_(x)—C, where M is selectedfrom the group consisting of copper (Cu), molybdenum (Mo), nickel (Ni)titanium (Ti), zinc (Zn), or antimony (Sb), and combinations thereof, M′is selected from the group consisting of titanium (Ti), vanadium (V),chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo),tungsten (W), or silicon (Si), and combinations thereof, and M′C_(x)—Cforms a matrix containing M_(y)Sn.

According to a third embodiment, the invention relates to an anodematerial with the general formula Mo₃Sb₇-C, where —C forms a matrixcontaining Mo₃Sb₇.

According to a fourth embodiment, the invention relates to an anodematerial with the general formula M_(y)Sb-M′C_(x)—C, where M may be anelectrochemically active metal and M′ may be another metal and whereM′C_(x)—C forms a matrix containing M_(y)Sb.

Other embodiments relate to anodes or rechargeable batteries containingthese materials as well as methods of making these materials usingball-milling techniques.

In the general formulas used herein, hyphens “-” indicate chemicalcompositions that are intermingled to form a composite material.Chemical bonds may or may not be present between these components of acomposite material.

The following abbreviations are commonly used throughout thespecification:

Li⁺—lithium ionLi⁰—elemental or metallic lithiumM_(y)Sb—metal antimonideCu₂Sb—copper antimonideMoSb—molybdenum antimonideM′O_(x)—metal oxideAl₂O₃—aluminum oxideSb₂O₃—antimony oxideM_(y)Sn—metal stannideM′C_(x)—metal carbideTiC—titanium carbideMo₃Sb₇—molybdenum antimonideCu₂Sb—Al₂O₃—C—copper antimonide aluminum oxide and carbon compositeCuSn—TiC—C—copper stannide titantium carbide and carbon compositeMo₃Sb₇-C—molybdenum antimonide and carbon compositeMoSb—TiC—C—molybdenum antimonide-titanium carbide-carbon compositeSEI—solid-electrolyte interfacialHEMM—high-energy mechanical millingXRD—X-ray diffractionXPS—X-ray photoelectron spectroscopySEM—scanning electron microscopyTEM—transmission electron microscopySTEM—scanning transmission electron microscopyEIS—electrochemical impedance spectroscopy

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, which relate toembodiments of the present disclosure. The current specificationcontains color drawings. Copies of these drawings may be obtained fromthe USPTO.

FIG. 1 provides XRD patterns of Cu₂Sb—C and Cu₂Sb—Al₂O₃—C nanocomposites.

FIG. 2 provides Al 2p, Cu 2p, and Sb 3d XPS data of an uncycledCu₂Sb—Al₂O₃—C electrode.

FIG. 3A provides an SEM image of Cu₂Sb—C. FIG. 3B provides an SEM imageof Cu₂Sb—Al₂O₃—C.

FIG. 4A provides TEM images of Cu₂Sb—Al₂O₃—C powder. FIG. 4B providesTEM images of Cu₂Sb—C powder.

FIG. 5A provides a voltage profile of Cu₂Sb—Al₂O₃—C. FIG. 5B provides adifferential capacity plot comparison of Cu₂Sb—Al₂O₃—C and Cu₂Sb—C at acurrent rate of 100 mA/g of active electrode material.

FIG. 6A provides cycle performance of Cu₂Sb—Al₂O₃—C from 0-2.0 V vs.Li/Li⁺ at 25° C. and a current rate of 100 mA/g of active electrodematerial. FIG. 6A provides cycle performance of Cu₂Sb—Al₂O₃—C andCu₂Sb—C at 55° C. and a current of 100 mA/g of active electrode materialbetween 0-2 V vs. Li/Li⁺. FIG. 6C provides rate capability comparison ofCu₂Sb—Al₂O₃—C and Cu₂Sb—C at 25° C. between 0-2 V vs. Li/Li⁺. FIG. 6Dprovides a comparison of Cu₂Sb—Al₂O₃—C discharged to 0 V and 0.5 V vs.Li/Li⁺ at 25° C. and a current rate of 100 mA/g of active electrodematerial. All current rates in FIGS. 6A-6D were calculated per gram ofactive electrode material.

FIG. 7 provides cycle performance of a Cu₂Sb—Al₂O₃—C and LiMn₂O₄ spinelpouch cell at 25° C. between 0-2 V vs. Li/Li⁺ at a current of 100 mA/gof active electrode material.

FIG. 8A provides EIS data for Cu₂Sb—Al₂O₃—C and Cu₂Sb—C nanocompositematerials before cycling. FIG. 8B provides EIS data for Cu₂Sb—Al₂O₃—Cand Cu₂Sb—C nanocomposite materials after the 1st cycle. FIG. 8Cprovides EIS data for Cu₂Sb—Al₂O₃—C and Cu₂Sb—C nanocomposite materialsafter the 20th cycle. FIG. 8D shows the circuit used to obtain the datain FIGS. 8A-C.

FIG. 9A provides TEM images of Cu₂Sb—Al₂O₃—C electrode material after 1,50 and 500 cycles. FIG. 9B provides TEM images of Cu₂Sb—Celectrodematerial after 1, 50 and 247 cycles.

FIG. 10A provides ex-situ XRD data for a Cu₂Sb—Al₂O₃—C electrode beforecycling. FIG. 10B provides ex-situ XRD data for a Cu₂Sb—Al₂O₃—Celectrode after 1 cycle. FIG. 10C provides ex-situ XRD data for aCu₂Sb—Al₂O₃—C electrode before cycling after 50 cycles. FIG. 10Dprovides ex-situ XRD data for a Cu₂Sb—Al₂O₃—C electrode after 500cycles.

FIG. 11 provides XRD patterns of a CuSn—TiC—C nanocomposite.

FIG. 12A provides a SEM image of CuSn—TiC—C. FIG. 12B provides a TEMimage of CuSn—TiC—C. FIG. 12C provides an STEM image of CuSn—TiC-C. FIG.12D provides an element map of Ti in CuSn—TiC—C. FIG. 12E provides anelement map of Sn in CuSn—TiC—C. FIG. 12F provides a composite elementmap of Ti and Sn in CuSn—TiC—C.

FIG. 13 provides a voltage profile and differential capacity plotCuSn—TiC—C at 25° C. and a current of 100 mA/g of active electrodematerial between 0-2 V vs. Li/Li⁺.

FIG. 14A provides the volumetric discharge capacity of CuSn—TiC—C andcommercial graphite from 0-2.0 V vs. Li/Li⁺ at 25° C. and a current rateof 100 mA/g of active electrode material. FIG. 14B provides thegravimetric discharge capacity of CuSn—TiC—C and commercial graphitefrom 0-2.0 V vs. Li/Li⁺ at 25° C. and a current rate of 100 mA/g ofactive electrode material. FIG. 14C provides the volumetric dischargecapacity of CuSn—TiC—C and commercial graphite from 0-2.0 V vs. Li/Li⁺at 55° C. and a current rate of 100 mA/g of active electrode material.FIG. 14D provides the rate capability comparison of CuSn—TiC—C andcommercial graphite at 25° C. between 0-2 V vs. Li/Li⁺.

FIG. 15 provides the volumetric and gravimetric discharge capacity ofCuSn—TiC—C and commercial graphite from 0.2 V-2.7 V (OCV) vs. Li/Li⁺ at25° C. and a current rate of 100 mA/g of active electrode material and adifferential capacity plot of the second cycle (inset).

FIG. 16 provides the equivalent circuit used for the impedancemeasurements and electrochemical impedance spectra (EIS) of theCuSn—TiC—C nanocomposite material before cycling (inset), after the 1stcycle, and after the 20th cycle.

FIG. 17A provides a TEM image of a CuSn—TiC—C electrodes after 0 cycles.FIG. 17B provides a TEM image of a CuSn—TiC—C electrodes after 20cycles. FIG. 17C provides a TEM image of a CuSn—TiC—C electrodes after50 cycles. FIG. 17D provides a TEM image of a CuSn—TiC—C electrodesafter 100 cycles. FIGS. 17E and 17F provide TEM images of a CuSn—TiC—Celectrodes after 200 cycles.

FIG. 18A provides an XRD pattern of CuSn—TiC—C powder before electrodeformation. FIG. 18B provides an XRD pattern of CuSn—TiC—C from anelectrode after 200 cycles. FIG. 18C provides an XRD pattern ofCuSn—TiC—C from an electrode after 100 cycles. FIG. 18D provides an XRDpattern of CuSn—TiC—C from an electrode after 50 cycles. FIG. 18Eprovides an XRD pattern of CuSn—TiC—C from an electrode after 20 cycles.FIG. 18F provides an XRD pattern of CuSn—TiC—C from an electrode after 0cycles.

FIG. 19 provides XRD patterns of Mo₃Sb₇ and Mo₃Sb₇-C compositematerials. The reflections marked with a closed triangle correspond toan MoO₂ impurity phase.

FIG. 20 provides the crystal structure of Mo₃Sb₇. The three types ofatoms in the structure are labeled as Sb1, Sb2, and Mo.

FIG. 21 provides high-resolution TEM images of Mo₃Sb₇-C, showing thehighly-crystalline nature of the material.

FIG. 22A provides an SEM image of a Mo₃Sb₇-C particle. FIG. 22B providesan STEM element map of a Mo₃Sb₇-C particle showing the distribution ofSb. FIG. 22C provides an STEM element map of a Mo₃Sb₇-C particle showingthe distribution of C. FIG. 22D provides an STEM element map of aMo₃Sb₇-C particle showing the distribution of Mo.

FIG. 23A provides an SEM image of Mo₃Sb₇-C. FIG. 23B provides an SEMimage of acetylene black. FIG. 23C provides an SEM image of Mo₃Sb₇-C.

FIG. 24A provides a voltage profile of Mo₃Sb₇-C. FIG. 24B provides adifferential capacity plot for Mo₃Sb₇-C.

FIG. 25A provides an XRD pattern of Mo₃Sb₇-C not previously included inan electrode. FIG. 25B provides an XRD pattern of an Mo₃Sb₇-C electrodethat has been discharged to 0.45 V vs. Li/Li⁺. FIG. 25C provides an XRDpattern of an Mo₃Sb₇-C electrode that has been fully discharged. FIG.25D provides an XRD pattern of an Mo₃Sb₇-C electrode that has been fullycharged. In FIG. 25, the reflections marked with a closed trianglecorrespond to the MoO₂ impurity phase.

FIG. 26 provides a comparison of the cyclability of Mo₃Sb₇, Mo₃Sb₇-C,and graphite at 0-2 V vs. Li/Li⁺ at a current of 100 mA/g activematerial.

FIG. 27 provides rate capability data of Mo₃Sb₇-C as compared to that ofgraphite. Charge rates are calculated as current per gram of activeelectrode material. Cycling was performed at 0-2 V vs. Li/Li⁺.

FIG. 28 provides cycle performance of a full cell with Mo₃Sb₇-C anodeand the spinel manganese oxide cathode at a current rate of 30 mA/gactive material.

FIG. 29A provides the EIS plots of the Mo₃Sb₇ and Mo₃Sb₇-C compositematerials after before cycling. FIG. 29B provides the EIS plots of theMo₃Sb₇ and Mo₃Sb₇-C composite materials after 1 cycle. FIG. 29C providesthe EIS plots of the Mo₃Sb₇ and Mo₃Sb₇-C composite materials after 20cycles. FIG. 29D provides the equivalent circuit used for the Mo₃Sb₇ andMo₃Sb₇-C composites used to obtain the data in FIGS. 29A-C and EIS plotsof the Mo₃Sb₇ and Mo₃Sb₇-C composite materials. FIG. 29D provides theequivalent circuit used for the measurements.

FIG. 30A provides an XRD pattern of Mo₃Sb₇-C after 1 cycle. FIG. 30Bprovides an XRD pattern of Mo₃Sb₇-C after 111 cycles.

FIG. 31 provides high-resolution TEM images of Mo₃Sb₇-C after 111charge-discharge cycles. The circles highlight isolated regions ofcrystalline Mo₃Sb₇ that are smaller than the crystalline regions presentin the uncycled Mo₃Sb₇-C material.

DETAILED DESCRIPTION

The current disclosure relates to four general types of anode materials,anodes and batteries containing such materials, and methods of makingthese materials. Although the anode materials are typically describedherein in their delithiated forms, when used in a rechargeablelithium-ion battery, they will additionally contain lithium ions (Li⁺)in amounts that will vary as the battery cycles through its charged anddischarged states. The number of Li⁺ that may be in any general chemicalformula will depend on the number of elections gained by the anodematerial when that battery is in a fully charged state as compared to afully discharged state.

M_(y)Sb-M O, —C Materials

The first type of anode material has the general formulaM_(y)Sb-M′O_(x)—C, where M may be a metal such as copper (Cu),molybdenum (Mo), nickel (Ni), titanium (Ti), or tin (Sn), or combinationthereof, or similar metals and combinations thereof, and where M′ may bealuminum (Al), magnesium (Mg), titanium (Ti), vanadium (V), chromium(Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zirconium(Zr), molybdenum (Mo), tungsten (W), niobium (Nb), or tantalum (Ta), orcombinations thereof, or similar metals and combinations thereof. In onespecific embodiment, the first type of anode material may have thegeneral formula Cu₂Sb—Al₂O₃—C.

In specific embodiments, the material may be present in the form of ananocomposite material in which crystalline particles of Cu₂Sb areembedded in a matrix of the other materials. Cu₂Sb particles may have anaverage diameter or size of 500 nm or less, 200 nm or less, 100 nm orless, or 50 nm or less. In particular, they may have an average diameterof between 1 and 20 nm.

In an anode material with the general formula M_(y)Sb-M′O_(x)—C, M_(y)Sbparticles provide electrochemical activity. These particles may benanostructured. In the Cu₂Sb portion of the Cu₂Sb—Al₂O₃—C embodiment, aconductive Cu framework supports the electrochemically active Sb. Inother embodiments, M_(y) may provide a similar conductive framework.M′O_(x), which may also be referred to as a ceramic oxide, may beamorphous or partially amorphous. The —C portion forms a conductivecarbon matrix with the M′O_(x). M_(y)Sb is dispersed within this matrix.

In one embodiment, the particulate nature of the M_(y)Sb portion of theM_(y)Sb-M′O_(x)—C anode material may not develop until after thematerial has been cycled in an electrochemical cell. In someembodiments, the particulate nature may not be present until thematerial has been cycled at least 50 or at least 100 times in anelectrochemical cell. Prior to that time, regions of crystallinity, butnot well-defined particles may be observed.

Materials of the general formula M_(y)Sb-M′O_(x)—C may reduce orminimize the effects of changes in volume as lithium ions enter andleave the material by blending nanostructured materials that areelectrochemically active towards lithium (M_(y)Sb) with materials thatare inactive towards lithium (M′O_(x) and —C) to form composite anodematerials. Although, in some embodiments, the nanostructured materialsmay offer shorter diffusion lengths for lithium ions and may accommodatethe strain due to volume changes during battery cycling, the largesurface-area-to-volume ratio resulting from the particles' small sizeand the high surface reactivity of these nanostructured materials may beproblematic. The addition of M′O_(x)—C to form an inactive matrix mayhelp buffer the volume change in the electrochemically active materialduring charge/discharge cycles. The M′O_(x)—C matrix may also reduceagglomeration of the M_(y)Sb particles, which is detrimental to batteryperformance.

Anode materials with the general formula M_(y)Sb-M′O_(x)—C typicallyoperate at potentials sufficiently higher than the potential at whichLi⁺ converts to Li⁰ to avoid plating of lithium metal on the anode, orto reduce the rate of plating to a rate sufficiently low to avoidfailure of the battery due to a short circuit during its expectedlifetime. The operational potential may also prevent or reduce formationof an SEI layer.

Anode materials of general formula M_(y)Sb-M′O_(x)—C may be used in abattery with an expected lifetime of thousands of cycles, for example atleast 1000 cycles, or at least 2000 cycles.

These anodes may exhibit a much higher gravimetric and volumetriccapacities than a graphite anode. For instance, they may have agravimetric capacity of between 380 and 650 mAh/g and a volumetriccapacity of between 450 and 1,000 Ah/L.

Such batteries may retain at least 70% of their gravimetric orvolumetric capacity after a large number of cycles such a thousand ormore cycles.

Anode materials with the general formula M_(y)Sb-M′O_(x)—C may have ahigh tap density of greater than 1 g/cm³.

Finally, anode materials with the general formula M_(y)Sb-M′O_(x)—C maybe resistant to poisoning by Mn contained in the cathode.

Anode materials with the general formula Cu₂Sb—Al₂O₃—C may besynthesized, in some embodiments, by mechanochemical reduction of Sb₂O₃with Al and Cu metals in the presence of carbon. The carbon may be froman elemental or polymeric carbon source. For instance, it may be in theform of acetylene black or another similar material. In a specificembodiment, the mechanochemical reduction may be carried out in asingle, one-step, high-energy mechanical milling (HEMM) process, whichis a type of ball-milling process. Similar methods may be used for othermaterials of the general formula M_(y)Sb-M′O_(x)—C.

M_(y)Sn-M′C_(x)—C Materials

The second type of anode material has the general formulaM_(y)Sn-M′C_(x)—C, where M may be a metal such as copper (Cu),molybdenum (Mo), nickel (Ni), titanium (Ti), zinc (Zn), or antimony(Sb), combinations thereof, or similar metals and combinations thereof,and where M′ may be titanium (Ti), vanadium (V), chromium (Cr), iron(Fe), cobalt (Co), nickel (Ni), molybdenum (Mo), tungsten (W), orsilicon (Si) or combinations thereof, or similar metals and combinationsthereof. In one specific embodiment, the second type of anode materialmay have the general formula CuSn—TiC—C.

In specific embodiments, the material may be present in the form of ananocomposite material. In particular, it may contain particles of CuSnwith an average diameter or size of 500 nm or less, 200 nm or less, 100nm or less, or 50 nm or less.

In an anode material with the general formula M_(y)Sn-M′C_(x)—C, M_(y)Snparticles provide electrochemical activity. These particles may benanostructured. In the CuSn portion of the CuSn—TiC—C embodiment, aconductive Cu framework supports the electrochemically active Sn. Inother embodiments, M_(y) may provide a similar conductive framework.M′C_(x) may be amorphous or partially amorphous. The —C portion forms aconductive carbon matrix with the M′C_(x). M_(y)Sn is dispersed withinthis matrix.

Materials of the general formula M_(y)Sb-M′O_(x)—C may reduce orminimize the effects of changes in volume as lithium ions enter andleave the material by blending nanostructured materials that areelectrochemically active towards lithium (M_(y)Sn) with materials thatare inactive towards lithium (M′C_(x) and —C) to form composite anodematerials. Although, in some embodiments, the nanostructured materialsmay offer shorter diffusion lengths for lithium ions and may accommodatethe strain due to volume changes during battery cycling, the largesurface-area-to-volume ratio resulting from the particles' small sizeand the high surface reactivity of these nanostructured materials may beproblematic. The addition of M′C_(x)—C to form an inactive matrix mayhelp buffer the volume change in the electrochemically active materialduring charge/discharge cycles. The M′C_(x)—C matrix may also reduceagglomeration of the M_(y)Sb particles, which is detrimental to batteryperformance.

Anode materials with the general formula M_(y)Sn-M′C_(x)—C typicallyoperate at potentials that are sufficiently higher than the potential atwhich Li⁺ converts to Li⁰ to avoid plating of lithium metal on theanode, or to reduce the rate of plating to a rate sufficiently low toavoid failure of the battery due to a short circuit during its expectedlifetime. The operational potential may also prevent or reduce formationof an SEI layer.

Anode materials of general formula M_(y)Sn-M′C_(x)—C may be used in abattery with an expected lifetime of thousands of cycles, for example atleast 1000 cycles, or at least 2000 cycles.

These anodes may exhibit volumetric capacity of at least 4 times higherthan that of a graphite anode. For example, such anodes may exhibit asecond cycle discharge capacity of >1,000 mAh/cm³.

Such batteries may retain at least 70% of their gravimetric orvolumetric capacity after a large number of cycles such as thousands ofcycles.

Anode materials with the general formula M_(y)Sn-M′C_(x)—C may have atap density of at least 2.0 g/cm³.

Finally, anode materials with the general formula M_(y)Sn-M′C_(x)—C maybe resistant to poisoning by Mn contained in the cathode.

Anode materials with the formula CuSn—TiC—C may be synthesized, in someembodiments, by first furnace heating a mixture of Sn and other metalsand then ballmilling the resulting compounds in the presence of carbonto achieve a mechanochemical reduction. The carbon may be from anelemental or polymeric carbon source. For instance, it may be in theform of acetylene black or another similar material. In a specificembodiment, the material is formed by first furnace heating a mixture ofSn, Cu, and Ti, and then ballmilling the resulting compounds in thepresence of carbon to achieve a mechanochemical reduction. Similarmethods may be used for other materials of the general formulaM_(y)Sn-M′C_(x)—C.

Mo₃Sb₇—C Materials

The third type of anode material has the general formula of Mo₃Sb₇-C.The material may be a composite including Mo₃Sb₇ uniformly dispersed ina conductive carbon matrix. The Mo₃Sb₇ may be in the form of highlycrystalline particles in the size range 500 nm or less, particularly of100 nm to 1 μm.

Particles of Mo₃Sb₇ in Mo₃Sb₇-C may constrain Sb via its crystalstructure, thereby preventing agglomeration of the Sb, which isresponsible for capacity fade in most Sb alloy electrodes. Mo₃Sb₇ alsoexperiences significant changes in volume during cycling.

The inclusion of the material in a carbon matrix reduces the effects ofthese volume changes. Mo₃Sb₇-C materials may have a discharge capacityof at least 500 mAh/g or at least 900 mAh/cm³. These materials mayexhibit a tap density of at least 1.5 g/cm³. Mo₃Sb₇-C anodes may operateat a voltage of above 0.5 V, which is sufficiently higher than thepotential at which Li⁺ converts to Li⁰ to avoid plating of lithium metalon the anode, or to reduce the rate of plating to a rate sufficientlylow to avoid failure of the battery due to a short circuit during itsexpected lifetime.

In one alternative embodiment, the material may further include anoxide, such as Al₂O₃, TiO₂, VO₂, MoO₂, or WO₂, to form a compositematerial.

Mo₃Sb₇-C composite material may be formed by first firing a mixture ofMo and Sb metals in a furnace to obtain Mo₃Sb₇. This material may thenbe placed in an HEMM process with carbon to form Mo₃Sb₇-C. The carbonmay be from an elemental or polymeric carbon source. For instance, itmay be in the form of acetylene black or another similar material.

M_(y)Sb-M′C_(x)—C Materials

The fourth type of anode material has the general formulaM_(y)Sb-M′C_(x)—C, where M may be an electrochemically active metal andM′ may be another metal. In one specific embodiment, the first type ofanode material may have the general formula MoSb—TiC—C. In specificembodiments, the material may be present in the form of a nanocompositematerial containing MSb in a matrix of M′C_(x) and —C. In particular, itmay contain particles of MSb with an average diameter or size of 500 nmor less, 200 nm or less, 100 nm or less, or 50 nm or less.

In an anode material with the general formula M_(y)Sb-M′C_(x)—C, M_(y)Sbparticles provide electrochemical activity. These particles may benanostructured. The —C portion forms a conductive carbon matrix with theM′C_(x). M_(y)Sb is dispersed within this matrix.

Materials of the general formula M_(y)Sb-M′C_(x)—C may reduce orminimize the effects of changes in volume as lithium ions enter andleave the material by blending nanostructured materials that areelectrochemically active towards lithium (M_(y)Sb) with materials thatare inactive towards lithium (M′C_(x) and —C) to form composite anodematerials. Although, in some embodiments, the nanostructured materialsmay offer shorter diffusion lengths for lithium ions and may accommodatethe strain due to volume changes during battery cycling, the largesurface-area-to-volume ratio resulting from the particles' small sizeand the high surface reactivity of these nanostructured materials may beproblematic. The addition of M′C_(x)—C to form an inactive matrix mayhelp buffer the volume change in the electrochemically active materialduring charge/discharge cycles. The M′O_(x)—C matrix may also reduceagglomeration of the M_(y)Sb particles, which is detrimental to batteryperformance. Anode materials with the general formula M_(y)Sb-M′C_(x)—Cmay be synthesized, in some embodiments, by a high-energy mechanicalmilling (HEMM) process. Anode materials with the formulaM_(y)Sb-M′C_(x)—C may be synthesized, in some embodiments, by firstfurnace heating a mixture of Sb and other metals and then ballmillingthe resulting compounds in the presence of carbon to achieve amechanochemical reduction. The carbon may be from an elemental orpolymeric carbon source. For instance, it may be in the form ofacetylene black or another similar material.

Anodes and Batteries

The invention also includes anodes made from any of the anode materialsdescribed above. Such anodes may include a metal or other conductivebacking and a coating containing the anode material. The coating may beformed by applying a slurry to the metal backing. The slurry andresulting coating may contain particles of the anode material. Althoughin many embodiments agglomerates may not be preferred, in otherembodiments the coating may include agglomerates of particles of theanode material. The anode may contain only one type of anode material,or it may contain multiple types of anode materials, includingadditional anode materials different from those described above. Thecoating may further include conductive agents, such as carbon.Furthermore, the coating may contain binders, such as polymeric binders,to facilitate adherence of the coating to the metal backing or tofacilitate formation of the coating upon drying of the slurry. In someembodiments the anode may be in the form of metal foil with a coating.

In another embodiment, the invention relates to a battery containing ananode including an anode material as described above. The anode may of atype described above. The battery may further contain a cathode and anelectrolyte to complete the basic components of an electrochemical cell.The cathode and electrolyte may be of any sort able to form a functionalrechargeable battery with the selected anode material. The battery mayfurther contain contacts, a casing, or wiring. In the case of moresophisticated batteries it may contain more complex components, such assafety devices to prevent hazards if the battery overheats, ruptures, orshort circuits. Particularly complex batteries may also containelectronics, storage media, processors, software encoded on computerreadable media, and other complex regulatory components.

Batteries may be in very traditional forms, such a coin cells or jellyrolls, or in more complex forms such as prismatic cells. Batteries maycontain more than one electrochemical cell and may contain components toconnect or regulate these multiple electrochemical cells.

Batteries of the present invention may be used in a variety ofapplications. They may be in the form of standard battery size formatsusable by a consumer interchangeably in a variety of devices. They maybe in power packs, for instance for tools and appliances. They may beusable in consumer electronics including cameras, cell phones, gamingdevices, or laptop computers. They may also be usable in much largerdevices, such as electric automobiles, motorcycles, buses, deliverytrucks, trains, or boats. Furthermore, batteries according to thepresent invention may have industrial uses, such as energy storage inconnection with energy production, for instance in a smart grid, or inenergy storage for factories or health care facilities, for example inthe place of generators.

EXAMPLES

The following examples are provided to further illustrate specificembodiments of the invention. They are not intended to disclose ordescribe each and every aspect of the invention in complete detail andshould be not be so interpreted.

Example 1 Formation of Cu₂Sb—Al₂O₃—C Nanocomposite Material andElectrodes and Coin Cells Containing this Material

Cu₂Sb—Al₂O₃—C nanocomposite and Cu₂Sb—C nanocomposite materials as wellas electrodes and coin cells using these materials in Examples 2-7herein were prepared as described in this Example 1.

A Cu₂Sb—Al₂O₃—C nanocomposite, according to an embodiment of the presentinvention was synthesized by a reduction of Sb₂O₃ (99.6% (purity), AlfaChem, Kings Point, N.Y.) with aluminum (99.97%, 17 μm (particle size),Alfa. Chem.) and formation of Cu₂Sb with copper (99%, 45 μm, AcrosOrganics, Geel, Belgium) metal powder in the presence of carbon(acetylene black) by a high-energy mechanical milling (HEMM) process, asillustrated below by reaction 1:

Sb₂O₃+2Al+4Cu→2Cu₂Sb+Al₂O₃ (ΔG°=−1023 kJ/mol)  (1)

The overall negative free-energy change makes the reduction reaction (1)spontaneous. The required quantities of Sb₂O₃, Al, and Cu were mixedwith acetylene black in an Sb₂O₃—Al—Cu:C weight ratio of 80:20. ControlCu₂Sb—C nanocomposite material without Al₂O₃ was obtained through atwo-step process: (i) stoichiometric amounts of Cu and Sb wereball-milled to form Cu₂Sb, and (ii) the resultant Cu2Sb powder wasball-milled with 20 wt, % acetylene black to form the Cu₂Sb—Cnanocomposite. All HEMM steps were carried out in a planetary ball mill(Fritsch Pulverisette 6 planetary mill) for 12 hours (h) at a speed of500 rpm at ambient temperature under argon atmosphere in hardened steelvials having an 80 cm³ capacity with steel balls (diameter: ½ and ¼ in.)in a ball:powder weight ratio of 20:1. The vials were sealed inside anargon-filled glovebox prior to milling.

Electrodes containing Cu₂Sb—Al₂O₃—C nanocomposite material for use inelectrochemical tests were prepared by coating a copper foil with aslurry that was composed of 70 wt. % Cu₂Sb—Al₂O₃—C powder as the activematerial, 15 wt. % carbon black (Super P) as a conductive agent, 15 wt.% poly(vinylidene fluoride) (PVDF) as a binder, andN-methylpyrrolidinone (NMP) as the solvent. Following the coating step,the copper foil was dried at 120° C. for 2 h under vacuum. CR2032 coincells were assembled in an argon-filled glovebox with the electrodesthus prepared, using Celgard polypropylene as a separator, lithium foilas the counter electrode, and 1 M LiPF₆ in ethylene carbonate(EC)/diethyl carbonate (DEC) (1:1 v/v) as the electrolyte.

Example 2 X-Ray Diffraction Analysis of Cu₂Sb—Al₂O₃—C NanocompositeMaterial

The phase analysis of the synthesized samples was performed with aPhillips

X-ray diffraction (XRD) system with Cu Kα radiation. XRD patterns of theCu₂Sb—Al₂O₃—C and Cu₂Sb—C nanocomposites are given in FIG. 1. Bothnanocomposites show broad reflections corresponding to Cu₂Sb (JCDPSPowder Diffraction File Card No. 22-601). No reflections correspondingto Al₂O₃ were observed in the case of Cu₂Sb—Al₂O₃—C, possibly due to anamorphous or poorly crystalline character of Al₂O₃.

In order to investigate any structural changes that occurred duringelectrochemical cycling, XRD data were collected from electrodes thathad been detached from cycled cells and covered with polyimide tape as aprotective film. XRD was performed on electrodes that had been cycled todifferent points in the charge/discharge cycle. The XRD patterns ofcycled Cu₂Sb—Al₂O₃—C electrodes after 1, 50, and 500 cycles support thenotion that the degree of crystallinity of Cu₂Sb—Al₂O₃—C increases withthe number of cycles (FIG. 10).

Example 3 SEM and TEM Analysis of Cu₂Sb—Al₂O₃—C Nanocomposite Material

The morphology, microstructure, and composition of the synthesizedpowders were examined with a JEOL JSM-5610 scanning electron microscope(SEM) system and a JEOL 2010F transmission electron microscopy (TEM)system.

The morphology and particle size of Cu₂Sb—Al₂O₃—C and Cu₂Sb—C wereinvestigated with SEM and TEM. SEM images of Cu₂Sb—Al₂O₃—C and Cu₂Sb—Cin FIGS. 3A and 3B show the sub-micron particle size distribution of thecomposite material. The overall particle sizes of the Cu₂Sb—Al₂O₃—C andthe Cu₂Sb—C materials are similar. The TEM images of Cu₂Sb—Al₂O₃—C (FIG.4A) show that the material is composed of 2-10 nm sized, crystallineCu₂Sb particles mixed with carbon. The Al₂O₃ in the Cu₂Sb—Al₂O₃—Cmaterial could not be observed with TEM. When compared to theCu₂Sb—Al₂O₃—C nanocomposite, the TEM of the Cu₂Sb—C material showscrystalline regions that are well defined (FIG. 4B).

TEM was also used to observe changes in crystallinity and morphology ofcycled electrodes. In order to understand the role of Al₂O₃ in providinga significant improvement in the cycle performance of Cu₂Sb—C,high-resolution TEM was performed on Cu₂Sb—Al₂O₃—C and Cu₂Sb—Celectrodes that had been cycled for different numbers of cycles. Cu₂Sb—Cwas observed after 1, 50, and 247 cycles. 247 cycles was chosen as thestopping point for the Cu₂Sb—C cell because Cu₂Sb—C already lost over50% of its stable capacity after 247 cycles. Cu₂Sb—Al₂O₃—C was observedafter 1, 50, and 500 cycles. At 500 cycles, the Cu₂Sb—Al₂O₃—C cell wasstill offering stable cycle performance and 99% coulombic efficiency.

The images in FIG. 9A show that after one cycle, the Cu₂Sb—Al₂O₃—Cmaterial is largely amorphous. There are some small regions ofcrystallinity, but the particle boundaries are not well defined. Afterone cycle, the Cu₂Sb—C electrode shows well-defined boundaries ofcrystalline spherical particles (FIG. 9B). After 50 cycles,Cu₂Sb—Al₂O₃—C has developed areas of crystallinity. After 50 cycles,Cu₂Sb—C has almost completely transformed into crystalline sphericalparticles that are embedded in a carbon matrix. After 500 cycles,Cu₂Sb—Al₂O₃—C has retained 94% of the capacity that was observed after50 cycles and has transformed into well-defined, 2-10 nm crystallineparticles that are almost entirely separate from one another and aresurrounded by a matrix of Al₂O₃ and carbon. After 247 cycles, theCu₂Sb—C material has already lost over 50% of the capacity that wasobserved at cycle 50. The size of the Cu₂Sb—C particles does notsignificantly change between cycles 50 and 247, but the Cu₂Sb—Cparticles appear to be tightly agglomerated after 247 cycles.

In summary, the presence of Al₂O₃ did not significantly change theparticle size or outer morphology of Cu₂Sb—C particles. However prior tocycling, based on XRD and microscopy data, the Cu₂Sb particles inCu₂Sb—C particles were found to be more crystalline than that inCu₂Sb—Al₂O₃—C. The presence of Al₂O₃ does not, however, significantlyinfluence the particle size or morphology. The Al₂O₃ matrix allows theCu₂Sb particles to remain separate yet electronically connected withinthe nanocomposite during cycling, thus reducing agglomeration andproviding the exceptional cycle life and lower impedance than isobserved with Cu₂Sb—C.

Example 4 APS Analysis of Cu₂Sb—Al₂O₃—C Nanocomposite Material

Surface characterization was performed on an uncycled Cu₂Sb—Al₂O₃—Celectrode with a Kratos X-ray photoelectron spectrometer (XPS) with amonochromatic Al Kα source. The uncycled Cu₂Sb—Al₂O₃—C electrode wasextracted from a coin cell in an argon-filled glovebox and transferredinto the XPS chamber via an argon-filled capsule. The surface of theelectrode was cleaned of surface oxides and electrolyte salts bysputtering with a 4 keV beam energy and an extractor current of 75 tofor 5.5 minutes.

The Cu₂Sb—Al₂O₃—C sample prepared in Example 1 was subjected to XPSanalysis and the results are shown in FIG. 2. There are two peaks in theAl 2p region. The peak at 75.2 eV corresponds to Al 2p in Al₂O₃ whilethe other peak at 77 eV corresponds to Cu 3p_(1/2). The Cu 2p_(3/2) peakin the Cu₂Sb—Al₂O₃—C sample occurs at 933.5 eV compared to 932.7 eVexpected for metallic copper. This shift in the Cu 2p_(3/2) bindingenergy indicates the absence of free metallic Cu and the presence of Cuto Sb bonding. The Sb 3d spectrum overlaps with the O 1s spectrum fromAl₂O₃. There are two pairs of peaks present for Sb 3d. The bindingenergies of the Sb(2) peaks match closely with that of metallic Sb,suggesting the presence of an amount of metallic Sb impurity althoughthe XRD data did not indicate metallic Sb. The Sb(1) peaks are at higherbinding energies than the Sb(2) peaks and are attributed to the antimonythat is bound to Cu in the Cu₂Sb alloy.

Example 5 Charge/Discharge, Tap Density, and Electrochemical CycleAnalysis of Electrodes Containing Cu₂Sb—Al₂O₃—C Nanocomposite Material

Charge/discharge experiments were performed galvanostatically at aconstant current density of 100 mA/g of active electrode material withina desired voltage range. Tap density measurements were made with aQuantachrome AT-4 Autotap machine. Electrochemical cycle testing at 25°C. was also performed with full, coffee-bag type cells with 4 Vmanganese spinet material as the cathode and lithium metal as thereference electrode.

The voltage profile and differential capacity plots (DCP) for theCu₂Sb—Al₂O₃—C nanocomposite are shown in FIG. 5. The Cu₂Sb—Al₂O₃—Cnanocomposite exhibits first cycle discharge and charge capacities of633 and 434 mAh/g, respectively, implying an irreversible capacity lossof 199 mAh/g and a coulombic efficiency of 68% in the first cycle. Afeature of the DCP, shown in FIG. 5B, is that there are three peaks onthe discharge portion of the plot and four peaks in the charge portionof the plot. This suggests that there may be an irreversible reactionthat takes place during the charging of the Cu₂Sb—Al₂O₃—C electrode. Itis also possible that the reaction mechanism during discharging isdifferent from the reaction mechanism during charging.

One of the significant features of Cu₂Sb—Al₂O₃—C anode material lies inthe cycle life. FIG. 6( a) shows the cyclability of Cu₂Sb—Al₂O₃—C over500 cycles. Cu₂Sb—Al₂O₃—C cycles well for 500 cycles at 99% coulombicefficiency. The presence of Al₂O₃ in the nanocomposite has a significantimpact on the cycle performance of Cu₂Sb—Al₂O₃—C as compared with thatof Cu₂Sb—C. As seen in FIG. 6A, Cu₂Sb—C alloy anodes are only stable forapproximately 100 cycles. The dramatic improvement in volumetriccapacity of Cu₂Sb—Al₂O₃—C over graphite is shown in FIG. 6A. Thehigh-temperature performance of Cu₂Sb—C was slightly better than that ofCu₂Sb—Al₂O₃—C. Both Cu₂Sb-based materials were stable for 100 cycles athigh temperature (FIG. 6B). When cycled at different charge rates,Cu₂Sb—C performs comparably to Cu₂Sb—Al₂O₃—C, but yields a higherdischarge capacity. A higher initial discharge capacity was observed forCu₂Sb—C cells during all other cycle tests as well. Both Cu₂Sb—C andCu₂Sb—Al₂O₃—C materials showed excellent rate capability. The cycleperformance of Cu₂Sb—Al₂O₃—C and Cu₂Sb—C at different charge rates isshown in FIG. 6C.

In summary, the Cu₂Sb—C alloy anode was found to show stable cycleperformance only to ˜100 cycles. Through the incorporation of Al₂O₃ into the alloy anode to form Cu₂Sb—Al₂O₃—C, the stable cycle performancewas extended from 100 cycles to 500. After one cycle and after 20cycles, the Cu₂Sb—Al₂O₃—C material showed lower surface,charge-transfer, and bulk resistances than those of Cu₂Sb—C.

Example 6 EIS Analysis of Electrodes Containing Cu₂Sb—Al₂O₃—CNanocomposite Material

Electrochemical impedance spectroscopic analysis (EIS) was conductedwith Solartron SI1260 equipment. A signal of 10 MV in amplitude wasapplied in the frequency range of 10 kHz to 0.001 Hz. In the EISmeasurements, the Cu₂Sb—Al₂O₃—C nanocomposite served as the workingelectrode, and lithium foil served as the counter and referenceelectrodes. The impedance response was measured after different numbersof charge-discharge cycles (after 0, 1, and 20 cycles) at 2 V vs.Li/Li⁺.

EIS measurements of Cu₂Sb—Al₂O₃—C and Cu₂Sb—C (both prepared asdescribed in Example 1) after 0, 1, and 20 cycles were performed inorder to further understand the electrochemical performance, and theresults are presented in FIG. 8. The EIS data were analyzed based on theequivalent circuit and variables shown in FIG. 8. R_(u) refers touncompensated resistance between the working electrode and the lithiumreference electrode, CPE_(s) refers to the constant phase element of thesurface layer, R_(s) refers to the resistance of the SEI layer, CPE_(dl)refers to the CPE of the double layer, R_(ct) refers to thecharge-transfer resistance, and Z_(w) refers to the Warburg impedance.Generally, the EIS spectrum can be divided into three frequency regions:low frequency, medium-to-low frequency, and high frequency, whichcorrespond to cell geometric capacitance, charge transfer reaction, andlithium-ion diffusion through the surface layer, respectively. The slopeof the impedance curve in the low frequency region is related tolithium-ion diffusion in the bulk of the active material.

Prior to cycling, Cu₂Sb—C has lower impedance than Cu₂Sb—Al₂O₃—C in allthree ranges of frequency (FIG. 8A). This behavior is expected due tothe fact that a larger weight percent of the Cu₂Sb—C electrode materialis made up of a copper-containing species and the Al₂O₃ in theCu₂Sb—Al₂O₃—C material is electronically insulating. Before eithermaterial is cycled, the curved portion of the impedance measurement isdominated by the charge-transfer resistance R_(ct), which is related tothe electrochemical reaction between the particles or the reactionbetween the electrode and the electrolyte. After one cycle (FIG. 8B),the shape of the impedance curves for both materials changes. Asemicircle is observed for each of the high and medium-to-low frequencyranges. The overall impedance of both materials has decreased comparedto the values observed before cycling, but the impedance of the Cu₂Sb—Cis higher than that of Cu₂Sb—Al₂O₃—C in the medium-to-low and lowfrequency ranges. After 20 cycles (FIG. 8C), the difference in theimpedance response of Cu₂Sb—C and Cu₂Sb—Al₂O₃—C is even moresignificant, and Cu₂Sb—Al₂O₃—C exhibits lower resistance in allfrequency ranges.

Example 7 Resistance of Cu₂Sb—Al₂O₃—C Nanocomposite Material toManganese Poisoning

One of the drawbacks to using carbon anode materials alongsidecommercial LiMn₂O₄ spinel cathodes is the poisoning of the anode by themanganese ions (Mn²⁺) that dissolve from the cathode lattice duringcycling. In order to test the resistance of Cu₂Sb—Al₂O₃—C to manganesepoisoning, 3-electrode pouch cells were constructed with Cu₂Sb—Al₂O₃—Cas the working electrode, 4 V manganese spinel material as the counterelectrode, and lithium metal as the reference electrode. The cycleperformance of the Cu₂Sb—Al₂O₃—C material in the pouch cell does notchange significantly from that of the coin cell, suggesting thatCu₂Sb—Al₂O₃—C anodes may be resistant to Mn²⁺ poisoning and can be usedwith manganese spinel cathodes in lithium-ion cells. The performance ofthe Cu₂Sb—Al₂O₃—C pouch cell is shown in FIG. 7.

Example 8 Formation and Analysis of Cu₆Sn₅—TiC—C Nanocomposite Materialand Electrodes and Coin Cells Containing this Material

Cu₆Sn₅—TiC—C material as anodes and coin cells containing this materialwere prepared and experiments were carried out in a manner similar tothat used for Cu₂Sb—Al₂O₃—C in Example 1 above. In particular,Cu₆Sn₅—TiC—C nanocomposite material was prepared by first obtaining amixture of Cu—Sn—Ti alloy phases by heating a mixture of Sn (99.8%, <45μm, Aldrich), Cu (99%, 45 μm Acros Organics), and Ti (99.99%, ˜325 mesh,Alfa Aesar) powders in an atomic ratio of 3:1:5 at 900° C. in a flowingArgon atmosphere for 12 h. The mixture of Cu—Sn—Ti phases was then mixedwith 20 wt % acetylene black and subjected to high energy mechanicalmilling (HEMM) for 40 h at a speed of 500 rpm in a vibratory mill atambient temperature under argon atmosphere to obtain the Cu₆Sn₅—TiC—Cnanocomposite.

Testing of this material shows desirable material properties similar tothose obtained with Cu₂Sb—Al₂O₃—C. In particular, the presence of Cu₆Sn₅in a conductive matrix of TiC and —C was verified as was the presence ofa Cu framework containing electrochemically active Sn particles. Theconductive matrix improves the cycle life of Cu₆Sn₅ as compared to theperformance data for Cu₆Sn₅ alone available in scientific literature.

Example 9 X-Ray Diffraction Analysis Cu₆Sn₅—TiC—C Nanocomposite Material

Samples were characterized with a Rigaku X-ray diffractometer with Cu Kαradiation, Hitachi S-5500 STEM, and JEOL 2010 TEM operating at 300 kV.The STEM and TEM samples were prepared by dispersing the sample inethanol, depositing it drop wise onto a carbon-coated copper grid, andremoving the ethanol at ambient temperature. The electrodes for theelectrochemical evaluation were prepared by mixing 70 wt % activematerial (Cu₆Sn₅—TiC—C) powder, 15 wt % carbon black (Super P), and 15wt % polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) to forma slurry. The slurry was spread onto a copper foil and dried at 120° C.for 2 h under vacuum. The electrodes were then assembled into CR2032coin cells in an Ar-filled glove box using Celgard polypropyleneseparator, lithium foil as the counter electrode, and 1M LiPF₆ inethylene carbonate (EC)/diethyl carbonate (DEC) (1:1 v/v) electrolyte.The discharge-charge experiments were performed galvanostatically at aconstant current density of 100 mA/g of active material within thevoltage range of 0-2.0 V vs. Li/Li⁺ or 0.2 V-OCV vs. Li/Li⁺ Cycletesting was performed at 25° C.

FIG. 11 shows the XRD pattern of the Cu₆Sn₅—TiC—C sample. This sampleexhibits peaks corresponding to crystalline Cu₆Sn₅ (JCPDS No.00-045-1488) and TiC (JCPDS No. 00-032-1383) and confirms the formationof Cu₆Sn₅ and TiC. The carbon in the composite is not highly crystallineand does not appear in the XRD pattern.

In order to better understand the changes in morphology of theCu₆Sn₅—TiC—C material during cycling, XRD was performed on electrodematerials that had been fully discharged down to 0 V vs. Li/Li⁺ andcycled between 0 and 200 cycles. After 200 cycles, the capacity of theCu₆Sn₅—TiC—C electrode had been reduced to less than one percent of theoriginal capacity. FIG. 18 shows the XRD patterns of Cu₆Sn₅—TiC—Celectrodes after up to 200 cycles. The XRD patterns do not changesignificantly for the electrodes that have been cycled, even after thematerial stops showing any appreciable capacity. This indicates that theparticles are not agglomerating or significantly changing in size.

Example 10 SEM and TEM Analysis of CuSn—TiC—C Nanocomposite Material

FIG. 12 shows the SEM, TEM, and STEM element mapping images of theCu₆Sn₅—TiC—C nanocomposite. The SEM image in FIG. 12A shows the largeparticles of carbon (acetylene), with the smaller Cu₆Sn₅ and TiCparticles blended and stuck to the carbon. The TEM image in FIG. 12Bshows the highly crystalline nature of a ˜30 nm Cu₆Sn₅ particle. Theparticle in the TEM image appears to be coated with a layer of eithercarbon or TiC, but lattice fringes could not be observed for TiC. Thedistribution of particle sizes observed via TEM was between 10 and 200nm. The STEM images shown in FIGS. 12D-F reveal presence of Ti on theCu₆Sn₅ particles. The TiC does not appear to be a homogenous coating onthe particles but rather is present as heterogeneous marbling on theoutside of the particles. TEM data from electrodes containingCu₂Sb—Al₂O₃—C that were cycled between 1 and 200 cycles shows thatCu₆Sn₅ particles do not agglomerate in the material and that themorphology of the particles does not change during extended cycling.

The cycled electrodes used in Example 9 further analyzed via TEM. Theresults of the XRD on cycled Cu₆Sn₅—TiC—C electrodes are furthersupported by the TEM images in FIG. 17. The TEM images show that themorphology and size of the Cu₆Sn₅ particles do not change significantlyduring cycling, even after the material has failed.

Example 11 Electrochemical Analysis of Cu₆Sn₅—TiC—C NanocompositeMaterial

The voltage profile and differential capacity plot of the Cu₆Sn₅—TiC—Cnanocomposite are shown in FIG. 13. When cycled between 0 and 2 V vs.Li/Li⁺, the nanocomposite exhibits first discharge and charge capacitiesof 797 and 629 mAh/g, respectively. When the material is cycled between0.2 V vs. Li/Li⁺ and the open circuit voltage (OCV) for the material,the first discharge and charge capacities are 321 mAh/g and 225 mAh/g,respectively, which indicates that the irreversible capacity loss is 96mAh/g and the coulombic efficiency is around 70%. The irreversiblecapacity loss may be largely associated with the reduction of theelectrolyte on the active material surface and the formation ofsolid-electrolyte interfacial (SEI) layer. The major peaks in thedifferential capacity plot (FIG. 13) when the material is cycled down to0 V vs. Li/Li⁺ occur around 0.35 V and 0.13 V vs. Li/Li⁺. When thematerial is cycled between 0.2 V vs. Li/Li⁺ and the open circuit voltage(OCV) for the material, only one peak is observed in the dischargecycle, at around 0.31V vs. Li/Li⁺ (FIG. 15, inset). This change in thedifferential capacity plot and the corresponding reduction in capacityindicate that the reaction of lithium with Cu₆Sn₅ is not complete whenthe material is discharged down to 0.2 V vs. Li/Li⁺ however a drasticimprovement in cycle life is observed. The improvement in cycle lifewhen the Cu₆Sn₅ material is kept above 0.2 V vs. Li/Li⁺ is likely due tothe avoidance of the significant structural changes that occur when Cuis extruded from the Cu₆Sn₅ material and replaced with additionallithium to achieve Li_(4.4)Sn.

Based upon the differential capacity plot, and the previously publishedreaction mechanism for Cu₆Sn₅, the reaction mechanism for theCu₆Sn₅—TiC—C material is as follows:

10Li+Cu₆Sn₅→5 Li₂CuSn+Cu  (1)

2.2Li+Li₂CuSn→Li_(4.4)Sn+Cu  (2)

This reaction mechanism is consistent with what has been published inthe literature for Cu₆Sn₅ materials. When the material is discharged to0.2 V vs. Li/Li⁺, step two of the above reaction mechanism does notoccur.

FIG. 14 compares the cyclability of Cu₆Sn₅—TiC—C and graphite atdifferent temperatures and rates of charge. Cu₆Sn₅—TiC—C shows avolumetric discharge capacity that is four times that of graphite, agravimetric discharge capacity that is twice that of graphite and stablefor 70 cycles when both materials are cycled between 0-2.0 V vs. Li/Li⁺at 25° C. and a current rate of 100 mA/g of active electrode material.At 55° C. and a current rate of 100 mA/g, as shown in FIG. 14C, thevolumetric capacity is less stable for Cu₆Sn₅—TiC—C than at 25° C., butit is three times the volumetric capacity of graphite. FIG. 14D comparesthe excellent rate capability of the Cu₆Sn₅—TiC—C nanocomposite withthat of graphite. Even at a rate of 5 A/g active material, Cu₆Sn₅—TiC—Cshows higher capacity than that of graphite.

In summary, the second cycle discharge capacity of the Cu₆Sn₅—TiC—C was1340 mAh/cm³ (610 mAh/g) and the tap density was 2.2 g/cm³. Thevolumetric capacity of Cu₆Sn₅—TiC—C is approximately 4.5 times higherthan a graphite anode. Cu₆Sn₅—TiC—C also exhibits low impedance(described in further detail in Example 12) and good rate capacity.

Example 12 EIS Analysis of Electrodes Containing Cu₆Sn₅—TiC—CNanocomposite Material

Electrochemical impedance spectroscopic analysis (EIS) was conductedwith a Solartron SI1260 impedance analyzer by applying a 10 mV amplitudesignal in the frequency range of 10 kHz to 0.001 Hz. Cu₆Sn₅—TiC—C servedas the working electrode and lithium foil served as the counter andreference electrodes. The impedance response was measured after zero,one, and 20 charge-discharge cycles at 2 V vs. Li/Li⁺.

To gain insight into the electrochemical performance of Cu₆Sn₅—TiC—C EISmeasurements were conducted at 2 V vs. Li/Li⁺ before cycling, after the1st cycle, and after the 20th cycle. The EIS data were analyzed based onan equivalent circuit given in FIG. 16. In FIG. 16, R_(u) refers touncompensated resistance between the working electrode and the lithiumreference electrode, CPE_(S) refers to the constant phase element of thesurface layer, R_(s) refers to the resistance of the SEI layer, CPE_(dl)refers to the constant phase element of the double layer, R_(ct) refersto the charge-transfer resistance, and Z_(w) refers to the Warburgimpedance. Generally, the EIS spectrum can be divided into threefrequency regions, i.e., low-frequency, medium-to-low-frequency, andhigh-frequency regions, which correspond, respectively, to the geometriccapacitance of the cell, the charge-transfer reaction, and thelithium-ion diffusion through the surface layer. The EIS spectrarecorded before cycling, after one cycle, and after 20 cycles in FIG. 16consist of two semicircles and a line. The diameter of the semicircle inthe high-frequency region (lowest Z′ values) is a measure of theresistance R_(s) of the SEI layer. The diameter of the semicircle in themedium-frequency region (middle Z′ values) is a measure of thecharge-transfer resistance R_(ct), which is related to theelectrochemical reaction between the particles or between the electrodeand the electrolyte. The portion of the impedance curve that has alinear slope is related to lithium-ion diffusion in the bulk of theactive material.

Before cycling (FIG. 16, inset), the Cu₆Sn₅—TiC—C sample exhibits R_(s),R_(ct), and bulk diffusion resistances that are all an order ofmagnitude larger than the resistances of the Cu₆Sn₅—TiC—C samples after1 or 20 cycles. After the first cycle, the SEI layer has formed and themajority of the irreversible capacity loss has occurred. As aconsequence to the formation of the SEI layer, the overall impedance inall frequency ranges decreases after the first cycle. After 20 cycles,the discharge capacity has begun to increase slightly, and this may bedue to a decrease in bulk diffusion and surface resistance. Whencomparing the charge transfer resistance between the first and 20^(th)cycle, it was observed that the charge transfer resistance of the samplethat had been cycled 20 times was higher, though not significantly. Anincrease in the charge transfer resistance after 20 cycles indicatesthat the electrochemical reactions between the particles or between theelectrode and the electrolyte are becoming more difficult.

Example 13 Formation of Mo₃Sb₇-C Material and Electrodes and Coin CellsContaining this Material

Mo₃Sb₇-C and Mo₃Sb₇ materials as well as electrodes and coin cells usingthese materials were prepared as described in this Example 13.

First, the Mo₃Sb₇ alloy powders were obtained by heating a mixture ofrequired amounts of Sb (99.9%, Aldrich, St. Louis, Mo.) and Mo (99.8%,Aldrich) powders at 780° C. in a flowing 5% H₂ atmosphere for 18 h. TheMo₃Sb₇ alloy obtained was then ground and sieved to eliminate particlesover 100 μm. The Mo₃Sb₇ powder with particle size <100 μm was then mixedwith 20 wt % acetylene black and subjected to high energy mechanicalmilling (HEMM) for 12 h at a speed of 500 rpm in a vibratory mill atambient temperature under argon atmosphere to obtain the Mo₃Sb₇-Ccomposite.

Electrodes for electrochemical evaluation were prepared by mixing 70 wt% active material (Mo₃Sb₇-C) powder, 15 wt % carbon black (Super P), and15 wt % polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) toform a slurry. The slurry was spread onto a copper foil and dried at120° C. for 2 h under vacuum. The electrodes were then assembled intoCR2032 coin cells in an Ar-filled glove box using Celgard polypropyleneseparator, lithium foil as the counter electrode, and 1M LiPF₆ inethylene carbonate (EC)/diethyl carbonate (DEC) (1:1 v/v) electrolyte.

Example 14 X-Ray Diffraction Analysis of Mo₃Sb₇-C Material

Samples were characterized with a Phillips X-ray diffractometer with CuKα radiation. FIG. 19 shows the XRD patterns of the Mo₃Sb₇ and Mo₃Sb₇-Csamples. Both samples exhibit sharp peaks corresponding to crystallineMo₃Sb₇ (JCPDS No. 019-0807), with a small peak corresponding to a traceamount of MoO₂ (JCPDS No. 032-0671), but without any peaks correspondingto Mo (JCPDS No. 004-0809), Sb (JCPDS No. 005-0562), or Sb₂O₃ (JCPDS No.005-0543), confirming the formation of Mo₃Sb₇. The unit cell consists offour Mo₃Sb₇ groups with a total of 12 Mo, 12 Sb1, and 16 Sb2 atoms and alattice parameter a=9.5713±0.0008 Å. Mo₃Sb₇ has the cubic Ir₃Ge₇structure consisting of two interlocking face-condensed antiprisms, asshown in FIG. 20. One of the interlocking antiprisms is formed by eightSb2 atoms that surround each Sb1 atom. Each Sb1 atom is also surroundedby two tetrahedra; one tetrahedron is made up of four Mo atoms, and theother is made up of four Sb1 atoms. The other interlocking antiprism isa distorted square antiprism composed of a Mo atom coordinated to fourSb1 and four Sb2 atoms at the corners. In this structure, the Sb2 atomsare coordinated to three Mo atoms, one Sb2 atom, and six Sb1 atoms.

To investigate the structural changes that may occur duringelectrochemical cycling, XRD data were collected on electrodes that hadbeen cycled and then extracted from their cells. In order to investigatethe structural changes that occur during electrochemical cycling, XRDdata were collected on electrodes that had been cycled and thenextracted from the cells. XRD patterns recorded with electrodesdischarged to 0.45 V vs. Li/Li⁺, fully discharged electrodes, and fullycharged electrodes are shown in FIG. 25. The data indicate the completedisappearance of the crystalline Mo₃Sb₇ phase at 0.45 V vs. Li/Li⁺,followed by the appearance of Li₃Sb when the electrode is in thefully-discharged state. When the electrode is then fully-charged, thecrystalline Mo₃Sb₇ phase reappears. If the Mo is extruded as Mo metalfrom Mo₃Sb₇ during the discharge process as with other antimony-basedalloy anode materials, then the XRD pattern would be expected to showpeaks for Mo metal along with that for Li₃Sb in FIG. 25C. However, FIG.25C does not show any peaks for Mo metal, suggesting either the Mo atomsremain in the framework of Li₃Sb or extruded as amorphous Mo metal.

In order to better understand the source of the capacity fade in theMo₃Sb₇-C sample, XRD was performed on electrode materials that had beencycled for greater than 100 cycles and showed severe capacity fade. FIG.30 shows the XRD patterns of Mo₃Sb₇-C after one cycle and after 111cycles. After one cycle (FIG. 30A), peaks for crystalline Mo₃Sb₇ werepresent in the XRD pattern. After 111 cycles (FIG. 30B), no peaks forcrystalline Mo₃Sb₇ were observed.

Example 15 SEM and TEM Analysis of Mo₃Sb₇-C Material

A Hitachi S-5500 STEM and a JEOL 2010 TEM operating at 300 kV were used.The STEM and TEM samples were prepared by dispersing the sample inethanol, depositing it dropwise onto a carbon-coated copper grid, andremoving the ethanol at ambient temperature. FIG. 21 shows the TEMimages of the Mo₃Sb₇-C composite. The TEM images and diffraction patternof Mo₃Sb₇-C show the highly crystalline nature of the material. The STEMimages shown in FIG. 22 reveal the sub-micron particle size and ahomogeneous distribution of Sb, Mo, and C in the Mo₃Sb₇-C composite. TheSEM images of Mo₃Sb₇-C and acetylene in FIG. 23 show the sub-micronparticle size distribution in the composite material, as well as thehomogenous distribution of carbon and the Mo₃Sb₇.

Also in order to better understand the source of the capacity fade inthe Mo₃Sb₇-C sample, high-resolution TEM was performed on electrodematerials that had been cycled for greater than 100 cycles and showedsevere capacity fade. From the TEM images in FIG. 31, small regions ofcrystalline Mo₃Sb₇ were detected, but are smaller and more isolated fromone another than in the uncycled Mo₃Sb₇-C sample. The TEM data suggeststhat the capacity fade observed with Mo₃Sb₇-C at higher number of cyclesis due to the breaking and separation of the large crystalline Mo₃Sb₇particles that are present before cycling.

Example 16 Charge Discharge, Tap Density and Electrochemical CycleAnalysis of Electrodes Containing Mo₃Sb₇-C Material

Discharge-charge experiments were performed galvanostatically at aconstant current density of 100 mA/g of active material within thevoltage range of 0-2.0 V vs. Li/Li⁺. Cycle testing was performed at 25°C. Pouch lithium-ion cells consisting of the Mo₃Sb₇-C anode and a spinelmanganese oxide cathode were also assembled and cycled at roomtemperature.

The voltage profile and differential capacity plot of the Mo₃Sb₇-Ccomposite are shown in FIG. 24. The composite exhibits first dischargeand charge capacities of 736 and 606 mAh/g, respectively, implying anirreversible capacity loss of 130 mAh/g and a coulombic efficiency of82% in the first cycle for the composite. The irreversible capacity lossmay be largely associated with the reduction of the electrolyte on theactive material surface and the formation of solid-electrolyteinterfacial (SEI) layer. The major peaks in the differential capacityplot (FIG. 24B), around 0.8 V vs. Li/Li⁺ for alloying and around 1.0 Vvs. Li/Li⁺ for dealloying, correspond to the reaction of lithium withantimony. The electrochemical reaction between amorphous carbon andlithium appears as a broad peak below 0.2 V vs. Li/Li⁺.

FIG. 26 compares the cyclability of Mo₃Sb₇, Mo₃Sb₇-C, and graphite at0-2 V vs. Li/Li⁺ at a current of 100 mA/g active material. While Mo₃Sb₇exhibits drastic capacity fade after 20 cycles, the Mo₃Sb₇-C compositeexhibits excellent cyclability to 70 cycles. Clearly, the addition ofcarbon to the Mo₃Sb₇ alloy improves the cycle performance significantlyby acting as a conductive buffer to the volume changes during cycling.However, the capacity of the sample begins to fade around 70 cycles.Although the gravimetric capacity of the Mo₃Sb₇-C anode is less than twotimes of commercially available graphite, the volumetric capacity isapproximately three times that of graphite due to the much higher tapdensity (1.75 g/cm³) compared to that of graphite (˜1 g/cm³). FIG. 27compares the rate capability of the Mo₃Sb₇-C composite with that ofgraphite. Although the volumetric capacity is higher, the Mo₃Sb₇-Ccomposites exhibit lower rate capability than graphite, but it could beimproved by optimizing the electrode fabrication process.

Example 17 EIS Analysis of Electrodes Containing Mo₃Sb₇-C Material

Electrochemical impedance spectroscopic analysis (EIS) was conductedwith a Solartron SI1260 impedance analyzer by applying a 10 mV amplitudesignal in the frequency range of 10 kHz to 0.001 Hz. Mo₃Sb₇-C served asthe working electrode and lithium foil served as the counter andreference electrodes. The impedance response was measured after one and20 charge-discharge cycles at 2 V vs. Li/Li⁺.

To gain insight into the electrochemical performance of Mo₃Sb₇ andMo₃Sb₇-C, EIS measurements were conducted at 2 V vs Li/Li⁺ beforecycling, after the 1st cycle, and after the 20th cycle. The EIS datawere analyzed based on an equivalent circuit given in FIG. 29D. In FIG.29, R_(u) refers to uncompensated resistance between the workingelectrode and the lithium reference electrode, CPE_(S) refers to theconstant phase element of the surface layer, R_(s) refers to theresistance of the SEI layer, CPE_(dl) refers to the constant phaseelement of the double layer, R_(ct) refers to the charge-transferresistance, and Z_(w) refers to the Warburg impedance. Generally, theEIS spectrum can be divided into three frequency regions, i.e.,low-frequency, medium-to-low-frequency, and high-frequency regions,which correspond, respectively, to the geometric capacitance of thecell, the charge-transfer reaction, and the lithium-ion diffusionthrough the surface layer. The EIS spectra recorded before cycling inFIG. 29 consists of one semicircle and a line. After the 1st cycle andthe 20th cycle, the EIS spectra in FIG. 29 consist of two semicirclesand a line. The diameter of the semicircle in the high-frequency region(lowest Z′ values) is a measure of the resistance R_(s) of the SEIlayer, but is not observed for either material before cycling has beenperformed. The diameter of the semicircle in the medium-frequency region(middle Z′ values) is a measure of the charge-transfer resistanceR_(ct), which is related to the electrochemical reaction between theparticles or between the electrode and the electrolyte. The portion ofthe impedance curve that has a linear slope is related to lithium-iondiffusion in the bulk of the active material.

Before cycling, the Mo₃Sb₇ sample exhibits a higher R_(ct) and bulkdiffusion resistance than the Mo₃Sb₇-C sample. The semicirclecorresponding to R_(s) cannot be observed in the impedance measurementsbefore cycling. After the first cycle, both the samples exhibit twodistinct semicircles, corresponding to R_(s) and R_(ct). The Mo₃Sb₇-Csample shows higher R_(s) than Mo₃Sb₇, due to the development of the SEIlayer. The growth of the SEI layer is more pronounced in the Mo₃Sb₇-Csample, most likely because of the carbon. The effects of a moresignificant SEI layer can also be seen in the larger first cycleirreversible capacity loss for Mo₃Sb₇-C compared to that for the Mo₃Sb₇sample (FIG. 26). R_(ct) and the bulk diffusion resistance of theMo₃Sb₇-C sample are higher than those of Mo₃Sb₇ after the first cycle,presumably because the Mo₃Sb₇ particles are not separated from oneanother by carbon. After the 20^(th) cycle, the bulk diffusionresistance of the Mo₃Sb₇ sample becomes greater than that of theMo₃Sb₇-C sample because the Mo₃Sb₇ electrode has already begun breakingdown and encountering significant capacity fade.

Example 18 Resistance of Mo₃Sb₇-C Material to Manganese Poisoning

Full pouch cells were also assembled with the Mo₃Sb₇-C composite as theanode and the spinel manganese oxide cathode to determine the resistanceof the Mo₃Sb₇-C electrode to poisoning by the dissolved Mn from thespinel cathode. The full cell with the Mo₃Sb₇-C anode and manganeseoxide spinel cathode shows good cyclability over 100 cycles, indicatingthe resistance of the Mo₃Sb₇-C composite to manganese poisoning (FIG.28). The slight difference in performance between the coin cell and thefull pouch cell after 70-80 cycles may be related to the differences inconstruction of the cells and the extent of compression and contact.

Although only exemplary embodiments of the invention are specificallydescribed above, it will be appreciated that modifications andvariations of these examples are possible without departing from thespirit and intended scope of the invention. For instance, numeric valuesexpressed herein will be understood to include minor variations and thusembodiments “about” or “approximately” the expressed numeric valueunless context, such as reporting as experimental data, makes clear thatthe number is intended to be a precise amount.

1. An anode material comprising the general formula M_(y)Sb-M′O_(x)—C,wherein M is selected from the group consisting of copper (Cu),molybdenum (Mo), nickel (Ni), titanium (Ti), or tin (Sn), andcombinations thereof, wherein M′ is selected from the group consistingof aluminum (Al), magnesium (Mg), titanium (Ti), vanadium (V), chromium(Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zirconium(Zr), molybdenum (Mo), tungsten (W), niobium (Nb), or tantalum (Ta), andcombinations thereof, and wherein M′O_(x)—C forms a matrix containingM_(y)Sb.
 2. The anode material of claim 1, wherein the material has thegeneral formula Cu₂Sb—Al₂O₃—C.
 3. The anode material of claim 1, whereinM_(y)Sb comprises particles with an average diameter of 500 nm or less.4. A rechargeable battery comprising an anode material comprising thegeneral formula M_(y)Sb-M′O_(x)—C, wherein M is selected from the groupconsisting of copper (Cu), molybdenum (Mo), nickel (Ni), titanium (Ti),or tin (Sn), and combinations thereof, wherein M′ is selected from thegroup consisting of aluminum (Al), magnesium (Mg), titanium (Ti),vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co),nickel (Ni), zirconium (Zr), molybdenum (Mo), tungsten (W), niobium(Nb), or tantalum (Ta), and combinations thereof, and wherein M′O_(x)—Cforms a matrix containing M_(y)Sb.
 5. The rechargeable battery of claim4, wherein the anode material has the general formula Cu₂Sb—Al₂O₃—C. 6.The rechargeable battery of claim 4, wherein M_(y)Sb comprises particleswith an average diameter of 500 nm or less.
 7. An anode materialcomprising the general formula M_(y)Sn-M′C_(x)—C, wherein M is selectedfrom the group consisting of copper (Cu), molybdenum (Mo), nickel (Ni)titanium (Ti), zinc (Zn), or antimony (Sb), and combinations thereof,wherein M′ is selected from the group consisting of titanium (Ti),vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni),molybdenum (Mo), tungsten (W), or silicon (Si), and combinationsthereof, and wherein M′C_(x)—C forms a matrix containing M_(y)Sn.
 8. Theanode material of claim 7, wherein the material has the general formulaCu₆Sn₅—TiC—C.
 9. The anode material of claim 7, wherein M_(y)Sncomprises particles with an average diameter of 500 nm or less.
 10. Arechargeable battery comprising an anode material comprising the generalformula M_(y)Sn-M′C_(x)—C, wherein M is selected from the groupconsisting of copper (Cu), molybdenum (Mo), nickel (Ni) titanium (Ti),zinc (Zn), or antimony (Sb), and combinations thereof, wherein M′ isselected from the group consisting of titanium (Ti), vanadium (V),chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), molybdenum (Mo),tungsten (W), or silicon (Si), and combinations thereof, and whereinM′C_(x)—C forms a matrix containing M_(y)Sn.
 11. The rechargeablebattery of claim 10, wherein the anode material has the general formulaCu₆Sn₅—TiC—C.
 12. The rechargeable battery of claim 10, wherein M_(y)Sncomprises particles with an average diameter of 500 nm or less.
 13. Ananode material comprising the general formula Mo₃Sb₇-C, wherein —C formsa matrix containing Mo₃Sb₇.
 14. The anode material of claim 13, whereinMo₃Sb₇ comprises particles with an average diameter of 500 nm or less.15. The anode material of claim 13, further comprising Al₂O₃, TiO₂, VO₂,MoO₂, or WO₂, wherein these oxides, in conjunction with —C, form part ofa matrix containing Mo₃Sb₇.
 16. A rechargeable battery comprising ananode material comprising the general formula Mo₃Sb₇-C, wherein —C formsa matrix containing Mo₃Sb₇.
 17. The rechargeable battery of claim 16,wherein Mo₃Sb₇ comprises particles with an average diameter of 500 nm orless.
 18. The rechargeable battery of claim 16, the anode materialfurther comprising Al₂O₃, TiO₂, VO₂, MoO₂, or WO₂, wherein these oxides,in conjunction with —C, form part of a matrix containing Mo₃Sb₇.
 19. Ananode material comprising the general formula M_(y)Sb-M′C_(x)—C, whereinM is an electrochemically active metal, M′ is a metal, and M′C_(x)—Cforms a matrix containing M_(y)Sb.
 20. The anode material according toclaim 19, wherein the material has the general formula MoSb_(x)—TiC—C,where the value of x is between 0 and
 1. 21. A rechargeable batterycomprising an anode material comprising the general formulaM_(y)Sb-M′C_(x)—C, wherein M is an electrochemically active metal, M′ isa metal and, M′C_(x)—C forms a matrix containing M_(y)Sb.
 22. Arechargeable battery according to claim 21, wherein the material has thegeneral formula MoSb—TiC—C.